The frequency of hamstring stretches required to maintain knee extension range of motion following an initial six-week stretching programme
Objective: The objective of this study was to determine the frequency of on-going hamstring stretching required to maintain knee extension ROM following an initial stretching programme.
Study Design: A test-retest randomised control trial with repeated measures was undertaken with 63 university-aged males as participants.
Background: Stretching exercises are commonly prescribed during warm-up and cool-down, and within training and rehabilitation programmes with a common aim to improve muscle extensibility and joint range of motion. Previous research has demonstrated that stretching the hamstring muscle group once a day, five days a week for a six-week period improves knee extension range of motion. However, it has been demonstrated that this improvement is short-lived and starts to reduce once the stretching intervention is ceased. To maintain the improvement in range of motion gained following an initial stretching programme, an on-going stretching programme may be required. There is, however, little research to demonstrate the optimal frequency of on-going stretching required to maintain the range of motion once the initial improvements have been achieved.
Method: Participants were randomly assigned to two intervention groups and a control group. The two intervention groups both stretched for 30 seconds three times, once per day, five days a week, for an initial six weeks. The intervention was an active knee extension static hamstring stretch in a supine position. After the six-week initial stretching programme, participants allocated to intervention group one continued stretching with the same stretching routine once a day, three days per week, and participants in intervention group two once a day, for one day per week, for a further six weeks. Participants in the control group did not stretch over the 12-week intervention period. Knee extension range of movement was assessed by an active knee extension test using an electronic goniometer at baseline, week six and week 12.
Results: Following the initial six-week stretching programme there was a significant (p < 0.05) improvement in knee extension range of motion (mean- 16.2 degrees) in both intervention groups. Over the further six-week on-going stretching programme those participants in intervention group one (stretched three days a week) maintained their improvement in range of motion, whereas those in intervention group two (stretched one day per week) did not. The difference between the groups was significant (p < 0.05). No significant difference (p > 0.05) was observed in knee extension range of motion in the control group.
Conclusion: The findings of this study were consistent with previous research that has demonstrated a six-week static hamstring stretching programme significantly improves the knee extension range of motion. The on-going hamstring stretching programme with the frequency of three times a week was required to maintain the initial improvement in knee extension ROM for 6 weeks. This finding may be useful to maintain the benefits of stretching exercises with minimal effort, and therefore potentially improve compliance with on-going stretching exercises.